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Summary Article: Ecology
from Science in the Contemporary World: An Encyclopedia

The study of biological organisms and their environment has been part of human inquiry from prehistoric times, but the effort gained an intellectual focus with the theory of natural selection developed by the English naturalist Charles Darwin (1809–1882). By the late nineteenth century, biologists, botanists, zoologists, and scientists from other disciplines were engaged in disciplined ecological studies. In the first half of the century, ecologists often viewed their subject matter in terms of an ecological community, though critics of this approach objected that ecological communities were difficult to define geographically because animal and plant species often participate in many different communities. Population ecology emerged as an alternative in the 1920s, attempting to create mathematical models of the population growth of individual species and predator-prey relationships. The idea of the carrying capacity of an environment to support certain levels of individuals of different species emerged. Experiments showed that microbes in solutions did not follow the mathematical models and that one species usually pushed out another species unless competition was somehow reduced. This discovery led to the related ideas of ecological niches and competitive exclusion, the theory that natural selection tended to reduce the potential for competition by rewarding the subdividing of resources into niches.

The British ecologist Arthur Tansley (1871–1955) coined the term ecosystem, and after World War II the ecosystem approach became influential. This approach initially emphasized biogeochemistry, following the movement of energy, chemicals, water, and resources through the food chain in a given environment to support plant and animal species. In a classic study, the English-born limnologist G. Evelyn Hutchinson (1903–1991) showed that guano deposits in South America increased fish populations and when fishermen from Peru and Chile shot the birds eating the fish, in an effort to get rid of their competitors, the fish populations actually decreased because fewer birds meant less guano.

During World War II, scientists and engineers became used to working with automatic control systems, with their feedback loops and self-adjusting characteristics: aircraft control systems, for example, and mechanical computers and gun control systems. The American mathematician Norbert Wiener (1894–1964) coined the term cybernetics in 1948 to describe the study of such systems. Ecosystem ecologists recognized that ecosystems were a form of cybernetic system and often used similar metaphors. The two brothers Eugene Odum (1913–) and Howard Odum (1922–) promoted the ecosystem approach, and an influential textbook by Eugene, Fundamentals of Ecology, first published in 1953, promoted the ecosystem concept and later used cybernetic metaphors. The Odums also worked for the Atomic Energy Commission (AEC) studying the impact of nuclear testing on Pacific islands.

The classic example of evolutionary ecology came from studies in the 1950s by the British naturalist H. B. D. Kettlewell (1907–1979) of the peppered moth, Biston betularia. Kettlewell pointed out that the darker forms of the moth were more common downwind from industrial sites in England than in areas where pollution was not so common. He argued that pollution had stained lichens on trees with soot and that when moths rested on the trees, the light-colored moths were eaten by birds and the darker-colored moths had a greater chance of survival. This study became a common example of the principle of natural selection in action. In the 1980s and 1990s, scientists found that Kettlewell’s technique contained flaws. Photographs from the study showed the moths on the trees, but Kettlewell used captured moths that he placed on trees, not realizing that that particular species of moth rarely lights on trees or that ornithologists doubted that the birds ate the moths when they were on the trees. The explanation that Kettlewell advanced is now abandoned, though the coloration frequency of moths in different areas has not been explained.

Spurred on by the writings of scientists like the biologist Rachel Carson (1907–1964), the environmental movement grew out of ecological concerns. As environmentalism gained strength, the demand for ecological studies increased and the field blossomed. In the 1970s, American universities began to grant degrees in ecology, whereas before, students interested in ecology graduated in biology, zoology, or botany. Ecology may be the most diverse and interdisciplinary of all scientific endeavors, with few scientists identifying themselves as just ecologists. The field is further subdivided by the type of organism primarily studied (plant ecology, animal ecology, or microbe ecology), the environment studied (marine ecology, tree ecology, or alpine ecology), or the methodology used (population ecology, community ecology, or ecosystem ecology).

The application of mathematical modeling, computer simulations, and thinking in terms of systems has grown since the 1940s to become a major part of the field of ecology. The web-of-life analogy so often used in teaching ecology has become a cliché, but it is accurate in that it suggests that the many parts that make up the whole of an ecosystem are connected to each other; it is also useful in the sense that removing a thread or threads weakens the overall web.

Stetson Bank at Flower Garden Banks National Marine Sanctuary in Georgia, one of the northernmost coral reefs in the United States. Coral reefs are very intricate ecosystems.

(National Oceanic & Atmospheric Administration/Frank and Joyce Burek)

Ecological studies are often small projects, but Big Science played a role in at least one project, the International Biological Programme (IBP), which began in 1961 in Amsterdam under the auspices of the International Union of Biological Sciences. The IBP began in earnest in 1968, and American ecologists obtained federal funding to participate in 1970. American ecologists explicitly used the ideas of cybernetics and systems ecology, and their usefulness to the environmental movement, to obtain the $40 million in funding. Much of the American funding went to creating computerized models of five biomes, such as the Eastern Deciduous Forest Biome and the Grassland Biome. The National Science Foundation (NSF) continued to fund ecological research after the official end of the IBP in 1974.

Scientists came to recognize that biodiversity is the foundation of a resilient ecology. By 2000, only about 1.75 million species, most of them insect species, had been identified worldwide. Estimates of the total number of species range from 3 million to 100 million, most of them yet to be found in tropical rainforests. The island of Madagascar is particularly rich in species unique to the island.

At the 1992 Earth Summit in Rio de Janeiro, an international agreement, the Convention on Biological Diversity (CBD), was adopted. The pact promoted the sustainable use of natural resources, preservation of species, and the equitable use of genetic resources. An overwhelming majority of nations signed and ratified the CDB; the United States only signed, and did not ratify, the treaty. Some Third World nations and indigenous peoples have asserted their right under the CDB to prevent scientists from conducting studies on territory that they control. They fear that a plant or other genetic resource might be found and developed into a commercial product without the nation or people receiving any compensation. Under the guidelines of the CDB, scientists must get prior informed consent or sign a bioprospecting agreement before conducting surveys or studies.

Scientists thought that the fundamental source of energy in all ecosystems was solar energy, but the discovery of life around deep-sea hydrothermal vents in 1977 provided an alternate ecological model, as well as perhaps an explanation of how the first life on Earth developed. Where the food chain of most other life on Earth starts with the process of photosynthesis, which converts sunlight into energy, species of bacteria around the vents use chemosynthesis to create energy, converting sulfides into organic carbon.

The microbiologist Lynn Margulis (1938–), who reinvigorated the idea of symbiosis, in which two different organisms intimately associate with each other, has championed the idea that microbes are the dominant form of life on Earth. This perspective inverts the classic way of viewing all species as forming a kind of pyramid of life with human beings at the top and changes the way ecosystems are viewed. Perhaps the ultimate expression of the idea of an ecosystem as a cybernetic system came when the biophysicist and inventor James Lovelock (1919–) developed the Gaia hypothesis in the late 1960s, arguing that Earth was like a living organism, maintaining surface and atmospheric conditions so that chemical processes and the temperature would sustain life. Margulis found the idea compatible with her own promotion of symbiosis and has vigorously championed Gaia. Many other biologists remain suspicious of such a holistic notion and are uncomfortable with Gaia’s mystical overtones.

See also Big Science; Biology and the Life Sciences; Carson, Rachel; Computers; Deep-Sea Hydrothermal Vents; Environmental Movement; Genetics; Global Warming; Lovelock, James; Margulis, Lynn; National Science Foundation; Oceanography; Symbiosis

  • Bocking, Stephen. Ecologists and Environmental Politics: A History of Contemporary Ecology. New Haven: Yale University Press, 1997.
  • Bowler, Peter J. The Norton History of the Environmental Sciences. New York: Norton, 1993.
  • Golley, Frank Benjamin. A History of the Ecosystem Concept in Ecology: More Than the Sum of the Parts. New Haven: Yale University Press, 1993.
  • Hagen, Joel B. An Entangled Bank: The Origins of Ecosystem Ecology. New Brunswick, NJ: Rutgers University Press, 1992.
  • Kingsland, Sharon E. Modeling Nature: Episodes in the History of Population Ecology. Chicago: University of Chicago Press, 1985.
  • Worster, Donald. Nature’s Economy: A History of Ecological Ideas. Second edition. New York: Cambridge University Press, 1994.
  • © 2005 by Eric G. Swedin

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